1. Field of the Invention
The present invention relates to a video device having a dual type imaging device.
2. Description of the Related Art
In human eyes, sensitivity for color is lower than that for luminance. Therefore, in a standard such as the NTSC (National Television System Committee) system, it is prescribed that the resolution for color is lower than that for luminance. Therefore, a G-and-R/B system is provided in a conventional dual-type imaging device. Such an imaging device has a first CCD (charge coupled device) which is provided with a filter F1, for passing green light, and a second CCD which is provided with a filter F2 which passes red and blue light to alternate light-sensitive elements. The filters F1 and F2 are shown in FIG. 1. Output signals of the first CCD and the second CCD are superposed on each other in an image signal processing circuit. Namely, a luminance signal is obtained from each light-sensitive element on the first CCD, and a color signal is obtained from each pair of light-sensitive elements on the second CCD in combination with the light-sensitive elements on the first CCD.
Thus, in the conventional device, since a color signal is obtained from information from pairs of light-sensitive elements (corresponding to two pixels) on the second (CCD, the amount of information for a color signal is not sufficient, in comparison with the information for a luminance signal, and a high-quality color image cannot be obtained. When such an image signal having a low quality, is inputted into a computer to carry out an image processing for each pixel, the deterioration of the image quality may be remarkable. To prevent the deterioration of the image quality from occurring, a triple type imaging device, in which three CCDs are provided, is used. A filter, for passing, red, green or blue light is placed on each of the CCDs. In this construction, however, the imaging device is bulky and the electronic circuits are complex.
On the other hand, conventionally, as a photometry device provided in a still-video camera, a device in which photometry (determination of the exposure value) is carried out by using a CCD provided for sensing an image is known. However, since the dynamic range of the CCD is narrow, the photometry data may not be within the dynamic range. In such a case, it is necessary that the photometry operation should be repeatedly carried out while changing the dynamic range until the photometry data is within the dynamic range, and thus, the exposure value cannot be determined quickly. Conversely, in a construction in which a sensor for measuring a daylight is provided on an outer surface of the camera body, since the photometry can be carried out with a broad dynamic range, the exposure value can be determined in a short time. However, this sensor is provided for measuring merely the daylight, and therefore, the measured area may not coincide with the object to be photographed. Accordingly, the exact photometry data may not be obtained by the sensor.